Global type versus Local type : Global Local « XML Schema « XML Tutorial

1. XML Tutorial
2. XML Schema
3. Global Local

Global declarations are declarations that appear as direct children of the <schema> element. 
Global element declarations can be reused throughout the XML Schema. 
Local declarations do not have the <schema> element.
Local types can be used only in their specific context. 

Referring to an Existing Global Element 

To refer to a global element declaration, include a ref attribute and specify the name of the global element as the value.

<element ref="target:first"/> 

An XML Schema Document Referencing Globally Defined Declarations

<xsd:schema
   xmlns:xsd="http://www.w3.org/2001/XMLSchema"
   elementFormDefault="qualified"
   targetNamespace="http://www.java2s.com/namespaces/pub"
   xmlns="http://www.java2s.com/namespaces/pub">

    <xsd:element name="publications">
      <xsd:complexType>
       <xsd:sequence>
        <xsd:element ref="book"/>
       </xsd:sequence>
      </xsd:complexType>
    </xsd:element>
    
    <xsd:element name="book">
      <xsd:complexType>
       <xsd:sequence>
        <xsd:element ref="title"/>
        <xsd:element ref="author"/>
        <xsd:element ref="description"/>
       </xsd:sequence>
       <xsd:attribute name="isbn" type="xsd:string"/>
      </xsd:complexType>
    </xsd:element>
    
    <xsd:element name="title" type="xsd:string"/>
    <xsd:element name="author" type="xsd:string"/>
    <xsd:element name="description" type="xsd:string"/>

</xsd:schema>